Janky behavior with imageEdit.scaleChanged() in inline image editor

Description

As noted in ticket:21391:39, there's some janky behavior when tabbing between the width and height scaling values in the inline image editor. Tabbing between values appears to increment the values down 1 unit at a time. Short screencast to illustrate: ​http://screencast.com/t/tPiq9KlYVzzj

My best guess is something with the imageEdit logic in image-edit.js. Javascript is not my forte.

You know... I bet it's a problem with rounding. Looks like it's probably floor-ing, which will keep ticking numbers down if it doesn't divide evenly. Just tried it on a square image and it didn't do that, but can reproduce on others. Not sure about a punt - does feel kind of buggy.